The interaction of light and other electromagnetic radiation with materials is well-studied. One important class of such interactions includes optoelectronic devices, e.g., photovoltaic devices in which exposure of the material to light causes separation of charge in the material, and the flow of electrical current. Typically, in such devices, only a single wavelength (or frequency) of radiation can be utilized by the device to produce current, thus the process is inherently somewhat inefficient. These or similar devices can also be used as radiation emitters, where current is applied, and radiation is emitted from the material, again typically at a single wavelength.